DB2创建VIEW的时候CHECK OPTION的作用
创建视图的时候有几种CHECK OPTIONCHECK OPTION
CASCADED CHECK OPTION
LOCAL CHECK OPTION
看看这个例子：
------------------------------ Commands Entered ------------------------------
CREATE TABLE tab1 (col1 SMALLINT );
CREATE VIEW v1 AS SELECT col1 FROM tab1 WHERE col1 > 20 ;
CREATE VIEW v2L AS SELECT col1 FROM v1 WITH LOCAL CHECK OPTION ;
CREATE VIEW v2C AS SELECT col1 FROM v1 WITH CASCADED CHECK OPTION ;
CREATE VIEW v3L AS SELECT col1 FROM v2L WHERE col1 < 50 ;
CREATE VIEW v3C AS SELECT col1 FROM v2C WHERE col1 < 50 ;
------------------------------------------------------------------------------
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
------------------------------ Commands Entered ------------------------------
INSERT INTO v1 VALUES (10);
------------------------------------------------------------------------------
DB20000IThe SQL command completed successfully.
------------------------------ Commands Entered ------------------------------
INSERT INTO v2L VALUES (5);
------------------------------------------------------------------------------
DB20000IThe SQL command completed successfully.
------------------------------ Commands Entered ------------------------------
INSERT INTO v2C VALUES (5);
------------------------------------------------------------------------------
INSERT INTO v2C VALUES (5)
DB21034EThe command was processed as an SQL statement because it was not a
valid Command Line Processor command.During SQL processing it returned:
SQL0161NThe resulting row of the insert or update operation does not conform
to the view definition.SQLSTATE=44000
------------------------------ Commands Entered ------------------------------
INSERT INTO v3L VALUES (50);
INSERT INTO v3C VALUES (50);
------------------------------------------------------------------------------
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
------------------------------ Commands Entered ------------------------------
INSERT INTO v3L VALUES (100);
INSERT INTO v3C VALUES (100);
------------------------------------------------------------------------------
DB20000IThe SQL command completed successfully.
DB20000IThe SQL command completed successfully.
CASCADED CHECK OPTION 的作用是让当前创建的视图继承它使用到的视图的过滤条件，其他就没有什么区别了，都是为了阻止INSERT和UPDATE不符合过滤条件的数据。
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